This invention relates generally to orthopedic devices for the feet, and relates more specifically to a foot stabilization device for controllling gait by limiting excessive pronation and assisting in resupination of the foot during walking or running.
Various orthopedic devices intended to support or control motion of the foot and ankle have been known for a number of years, and by way of example, several forms of such devices can be found in U.S. Pat. Nos. 1,283,335; 1,565,259; 1,788,852; 2,292,643; 2,358,966; 2,708,930; 3,504,668; 3,867,930; and 4,084,586.
A normal human gait cycle consists of three phases: the contact phase in which the heel alone initially makes contact with the ground, the mid-stance phase in which the entire sole or plantar surface of the foot is in contact with the ground, and the propulsive phase wherein the balls of the foot and the toes push off. During the gait cycle, the foot and ankle tend naturally first to undergo movement known as pronation and then to move in a manner known as supination. While these movements of the foot and ankle are complex and can only be accurately described with reference to the three conventional anatomical planes (i.e., the sagittal, frontal and transverse planes), in simple terms pronation is an inward rolling and supination is an outward rolling of the foot and ankle.
More specifically, pronation and supination of the foot and ankle are a function primarily of the subtalar joint and the midtarsal joints. The subtalar joint is defined as the articulation between the talus and calcaneus (heel) bones. The midtarsal joints comprise the calcanealcuboid joint, which is defined as the articulation of the calcaneus and cuboid bones, and the talar-navicular joint, which is defined as the articulation of the talus (ankle) and the navicular bones. The navicular bone forms part of the arch structure.
A certain amount of pronation of the foot during walking or running is desirable. Generally speaking, pronationn occurs during the contact phase and about the first half of the mid-stance phase of a normal gait cycle. In the pronated position, the bones of the foot tend to become mobile or loose relative to one another so that the plantar surface can adapt to possibly uneven terrain. During the last half of the mid-stance phase and during the propulsive phase, however, resupination is essential so that the bones of the foot become relatively stable or locked to enable one to push-off.
Although some pronation is normal, many persons are troubled by excessive pronation in which the foot and ankle roll too far inwardly and the bones of the foot become hypermobile relative to one another. The combination of excessive pronation and resupination during a gait cycle can result in exaggerated back and forth rotational movement of the leg and knee with accompanying results that are highly undesirable. For example, various forms of muscular fatigue in children (sometimes called "growing pains") and in adults (such as back pain and leg fatigue) have been traced to excessive pronation. Likewise, excessive pronation has been found to be a cause of arch strain, heel pain, pain in the knee joint and the patella (knee cap), and foot deformities such as bunions and hammer toes (which in turn can result in corns and calluses). The effects of excessive pronation are particularly a problem for athletes, including those who run or jog.
Despite the existence of the aforementioned orthopedic devices, the most commonly attempted solution to the problem of excessive pronation has been use of conventional arch support wedges. This is believed to be because pronation is accompanied by a general stretching and flattening of the arch, and persons with flattened arches tend to suffer more frequently from the effects of excessive pronation. Use of arch support wedges has been found to be a generally ineffective solution, however, because it is directed to a sympton rather than the source of the problem. Some persons have flattened arches and do not excessively pronate; other persons with raised arches suffer greatly from the effects of excessive pronation. Rather than being due to flattened arches, excessive pronation is primarily the result of the internal structure of the foot and ankle, and in particular the motions of the subtalar and midtarsal joints; it is also influenced by external forces generated by knock-kneed, pigeon-toed or duck walking, for instance. Arch support wedges cannot control these factors, particularly in a person with naturally high arches, and even feet characterized by flattened arches will tend to roll right over conventional arch support wedges. Moreover, arch support wedges require shoes and thus are impractical for certain athletes such as dancers.
Another approach to the problem has been to carefully wrap adhesive tape circularly around the arch and to connect it with tape extending rearwardly along each side of the foot and around the heel. The tape extending around the heel serves to maintain the circular portion in position and to act as a lateral restraint on foot motion thereby preventing excessive pronation. To be effective, however, the tape must be applied very carefully in a prescribed manner by a qualified professional. Thus, this solution is not adapted for ordinary self-application. Also, tape has the disadvantage of stretching after a short time and any particular taping can last at most a few days. Further, the direction of pull and pressure cannot be adjusted after wrapping. In addition, tape does not assist in resupination of the foot. Tape also is irritating and cannot be used over.
The primary objective of the present invention is a more effective method and apparatus, which is capable of self-application, for restricting excessive pronation and assisting in resupination to control gait and thereby minimize resulting problems. The present invention clearly fulfills this objective.